1. Field of the Invention
The present invention relates generally to a control circuit for a vending machine, and more particularly pertains to a rather advanced control circuit for a vending machine having significantly improved features over vending machine control circuits available in the prior art.
2. Discussion of the Prior Art
The prior art is replete with many designs for vending machine control circuits, most of which include significant quantities of hard wiring therein to accomplish their various control and record keeping functions. Furthermore, the control and record keeping functions were often very limited in nature because of the manner in which pricing decisions and vending controls were executed.
Vending machines generally known in the prior art have often used electro-mechanical devices, such as relays and the like, for control of the dispensing functions. A typical control sequence is initiated by the insertion of coins into a coin mechanism which delivers a switch closure signal when sufficient coins have been inserted to vend a product. The credit signal is stored in an electromechanical relay. While storing the credit signal, this relay may close a circuit which provides power to a number of selector switches which can then in turn be operated to cause other relays to energize the mechanisms dispensing a product. Provisions are made in the circuitry so that only one selection can be made by the customer for every credit signal supplied by the coin mechanism, and a selection then cancels the stored credit signal.
The electromechanical devices which provide the necessary logic for operation of a vending machine of this nature are subject to many shortcomings. The mechanical parts are subject to wear, and require frequent adjustments. The correct operation of the system depends upon all parts functioning in a close timed relationship. The relatively slow moving mechanical parts frequently do not stay in a correctly timed relationship and may lose the established credit, resulting in a loss of money to the customer. A loss of the timing function may also fail to cancel credit after a selection has been made, resulting in a substantial loss of revenue to a merchant. Another problem arising from the slowness of the mechanical parts is that in some instances it is possible to "trap" the credit signal and effect the release of merchandise in excess of the amount equal to the established credit by manipulation of the electrical power applied to the machine or by rapid operation of the selector switches, or by other physical abuses of the machine causing shock and/or vibrations to the various mechanisms.
The prior art also discloses many multi-price vending control circuits sometimes called changers which control product delivery and also make change or refunds. Some of the known devices also have some price selectivity and other capabilities such as providing escrow, product selection, refunding and so forth. Control circuits are also known which make comparisons between amounts deposited or otherwise entered in a machine and a vend price. However, many of these prior art arrangements do not provide a vending control circuit which is able to provide almost unlimited price and product selection and at the same time control the product delivery and other control functions using relatively simple circuit and wiring arrangements.
Several of the known circuit arrangements have included various electronic and other types of accumulator means in their vending and refunding portions, and have also employcd logic circuitry for various purposes. However the present control circuit, while performing many functions performed by known control circuits, constitutes a new generation of such circuits which substantially enlarges the operating capability and flexibility of such circuits and includes features including particularly logic and memory circuit features which are different from anything known or available in the prior art.
In greater particularity, Lee U.S. Pat. No. 4,034,839 discloses a vending and price selection control circuit in which selection switches are actuable by a customer to produce one of a plurality of possible vends at different vend prices. Control and logic circuitry enter pricing information, apply power to a selected vend operator member, and also perform other vend and refund functions. The control circuit includes a coin switch or other type of credit entry unit, a payback switch circuit, a pulse generator circuit, and a comparator circuit. The comparator circuit includes a first accumulator portion in which amounts are totalized representing deposits made during each vending operation, and a second accumulator portion which is the pricing portion in which the vend price of a selected item or service is entered. The second accumulator also has amounts entered equal to the value of each coin refunded during a payback operation. Pricing entries are in the form of binary price codes in this disclosed arrangement.
Douglass U.S. Pat. No. Re. 28,749 discloses a control circuit for a vending machine which includes an input portion having coin actuated nickel, dime and quarter switches. A cam activated payback switch is also provided, and is located near the payback motor. The coin switches are connected to input terminals of associated logic circuits. Entries are made in binary form in an accumulator after passing through associated logic gating circuitry therein. The specification of this patent states that the entire circuit can be constructed of a few IC chips, some, if not all of which are available as off-the-shelf items.